The invention relates to improvements in apparatus for transporting streams or analogous accumulations of particulate materials. More particularly, the invention relates to improvements in apparatus which can be utilized with advantage for the transport of streams of comminuted tobacco leaves (such as cut ribs and/or shredded tobacco leaf laminae) in so-called rod making machines.
A modern cigarette rod making machine comprises an upwardly extending duct serving to deliver an ascending shower of comminuted tobacco leaves, reconstituted tobacco and/or artificial tobacco into an elongated channel having a foraminous top wall constituted by the lower reach or stretch of a driven endless belt or band. The upper side of the lower stretch advances along the underside of a stationary suction chamber so that the underside of such lower stretch can attract tobacco particles which form a growing stream advancing first past a suitable surplus removing trimming or equalizing device and thereupon into a wrapping mechanism to be draped into a continuous web of cigarette paper or other suitable wrapping material. The thus obtained continuous cigarette rod is severed to yield a file of plain cigarettes of unit length or multiple unit length which are ready to be transported to storage, to a packing machine or to a so-called filter tipping machine serving to assemble plain cigarettes with suitable filter mouthpieces for tobacco smoke.
Transporting apparatus of the above outlined character are also known as suction belt or band conveyors. The suction chamber is relatively long because the lower stretch of the endless foraminous belt must advance tobacco particles through an elongated stream building zone, thereupon past the trimming device, and thereafter all the way to the running web of cigarette paper or another strip or web of wrapping material in the aforementioned wrapping mechanism. The lower stretch of the rapidly advancing belt (a modern cigarette rod making machine is designed to turn out well in excess of 10,000 cigarettes per minute) is subject to pronounced wear as a result of frictional rubbing contact with the adjacent stationary parts of the apparatus; and this also holds true for the guide (such as the perforated bottom wall of the suction chamber) which compels the lower stretch of the belt to advance along a predetermined path past the stream building and trimming stations and all the way to the wrapping station.
Apparatus of the above outlined character are disclosed, for example, in U.S. Pat. Nos. 4,344,526 and 4,805,641 as well as in British Patent No. 974,821. The disclosures of all patents referred to in this specification are incorporated herein by reference.